The present invention concerns a multicolored, specifically a two-colored foil of thermoplastic synthetic material and a method and/or a device for the manufacture of the multicolored plastic foil.
Two-colored plastic foils are employed for example in motor vehicle technology as linings and surfaces for dashboards, interior roof linings or interior door panellings.
A two-colored dashboard foil or armature board foil of this type is described in DE 195 30 757 A1. The known foil consists of a sub-foil and at least two top foils, which have different colors and which are placed next to each other onto the plane sub-layer in order to form a two-color composite foil. The known dashboard foil is manufactured by co-extrusion of multiple extrusion of sub-layers and the two top layers, whereby a separate extruder is used for each of the layers. The plastified synthetic melts produced by the individual extruders are passed to an adapter block, which initially forms the individual layers separately, then joins same and finally discharges the combined layers via a sheet orifice. Consequently, in order to manufacture the known two- or multicolored plastic foil, at least three extruders are needed, which must be charged and controlled simultaneously. Moreover, in manufacturing the known foil, the reject rate is increased due to the great number of adjacent surfaces, for example for a two-colored foil, three adjacent surfaces between the different layers, where, for example, objectionable air-or gas bubbles can be occluded during the joining of layers, as well as other border area problems, which may occur for example based on minor differences in the properties of the synthetic materials employed for the individual layers.
It is the object of the present invention to provide a simple method for the manufacture of a two- or multicolored composite foil of thermoplastic synthetic material, with which it is possible to overcome the cited drawbacks of the state of the art. Furthermore, it is the object of the present invention to make available a device for implementation of the method. Another object of the invention lies in making available a two- or multicolored composite foil of thermoplastic synthetic material, which is easy to process further.
These objects are solved by the method according to claim 1, and also by the device according to claim 7 and the composite foil according to claim 19.
The method according to the invention in accordance with claim 1 for the manufacture of the multicolored, specifically two-colored, composite foil of the present invention comprises accordingly the manufacture of a carrier foil or carrier layer by extrusion of a thermoplastic synthetic material, whereby the carrier foil or the carrier layer has a least one depression or recess or indentation in its thickness profile.
The term depression in this context specifically means any deviation in the thickness profile of the carrier layer from its rectangular form. The depression can for example have the form of a rectangularly shaped recess or a rectangular cut-out from a rectangularly shaped contour. The cross-sectional contour passes at one top side of the carrier layer in form of a step into the depressed area of the recess. The depression can occupy one single closed area of the carrier foil, it can, however, also involve several, from each other separated, areas of the carrier foil.
Concurrently with the manufacture of the carrier layer, in the method according to the invention, at least one top foil or top layer is conducted, whereby the top layer or the top layers fits (fit) into the appropriate depression of the carrier layer and is/are positioned in such manner in the depression of the carrier layer or carrier foil, so that the thus obtained multicolored plastic foil of the invention is formed with flush surface, whereby the carrier layer has a different color or is dyed differently than the top layer or the top layers. It is also possible to guide several top layers or top foils from differently dyed synthetic materials.
The plastic foil or deep-drawn foil according to the invention produced with this method according to claim 19 has one top side and consists of a composite of one carrier layer or carrier foil and at least one top layer or top foil, whereby the top layer or top foil is fitted into a depression of the carrier layer or carrier foil and is flush with the surface of the carrier layer or carrier foil and the carrier layer or carrier foil and the top layer or top foil each form part of the top side of the foil and each have a different color shade.
The foil according to the invention preferably has a rectangular thickness profile, whereby the depression of the carrier foil or carrier layer is a rectangular recess and extends into the top foil or top layer arranged in the rectangular recess at the top side of the foil.
If one examines the top side or the upper surface of the finished foil of the invention, one sees, for example, with a two-colored foil, an area with a first color and an area with a second color. The first visible surface area belongs for example to the carrier layer and the second visible surface area is then a component of the top foil or top layer. The first color can have a dark, black or gray color shade while the second color can have a light or white shade of color.
Since the carrier layer or the carrier foil itself is visible with employment of the foil according to the invention, at least one extruder is saved by means of the present invention vis-a-vis the state of the art, as a result of which a most cost efficient and easier controllable method is obtained for producing the multicolored foil according to the invention. In addition, less waste is generated in the production of the foil according to the invention, since, for example, with a two-colored foil, which, according to the invention is composed of one carrier layer and only one top layer, there exists only one border area, compared with the above explained state of the art, which is technologically easier to control, as a rule, and contributes to reduced faulty production at the border areas, and thus to lower reject material.
Finally, it should be pointed out that, overall, the foil according to the invention has improved stability when applied or further processed, inasmuch as due to the minimal layer- and border area number, defects in the border area are also minimal.
The synthetic material from which the carrier layer or the carrier foil is made and the plastic material or plastic materials from which the top layer or the top layers is/are made preferable have approximately the same viscosity at the same temperatures. Because of said property, a stable compound of carrier layer and at least one top layer or top foil is obtained during manufacture of the foil according to the invention.
Suitable thermoplastic synthetic material for the method according to the invention are, among others: polyolefins, vinylpolymers, polyamides, polyesters, polyacetates, polycarbonates and, partially, polyurethanes as well. Specifically preferred are polyolefins.
The polychromacity of the plastic foil according to the invention can be obtained by adding suitable different color pigmentation or dye to the plastic melts of the carrier layer or the carrier foil and the top layer or top layers.
The device according to the invention for the manufacture of the foil according to the invention having two or more colors according to claim 7 comprises one extruder device for producing a plastified synthetic material melt, said extruder device being equipped with a first molding tool for molding a carrier foil or a carrier layer of a first color while forming at least one indentation.
It can have, in addition, at least one other extruder device for producing at least one additional plastified synthetic material melt, whereby at least the one additional extruder device is equipped with one additional molding tool for molding a respective top foil or top layer with a color different from the named first color, whereby at least the one additional molding tool is designed in such manner that the surface of the therefrom formed top layer or top foil respectively fits surface-flush into the corresponding depression of the carrier layer or carrier foil.
Furthermore, the device has a calender for surface-flush joining of the carrier foil or carrier layer with at least the one top layer or top foil fitted into the corresponding depression of the carrier layer or carrier foil and for smoothing out the produced surface.
The first molding tool preferably has a slot-like orifice, into which projects a protrusion, whose cross-section extending cross-wise vis-a-vis the flow direction of the plastic melt corresponds to the cross section of the depression of the to be produced carrier foil.
Said protrusion may be arranged adjustably in the first molding tool of the device according to the invention in order to be able to change or adjust the shape or the dimensions of the depression in the carrier foil or the carrier layer.
The protrusion can have the shape of a relatively elongated lip or lamella, which extends over a portion of the slot-like cross-section of the orifice of the first molding tool. It is possible, hereby, to thus produce a depression or recess in the carrier layer which is rectangular in cross-section.
The lip may be adjustable in height and/or in length, in order to be able to determine or vary the thickness or the size of the rectangular recess or the width of the recess and thus the width of the area of the foil according to the invention with the second color.
The orifice of the second molding tool can have a cross section extending cross-wise vis-a-vis the flow direction of the plastic melt, which corresponds approximately to the protrusion or the lip.
The interior cross-section of the orifice of the second and/or each additional molding tool is adjustable or variable in accordance with the selected adjustment of the projection or the lip of the first molding tool, so that an inside cross-section of the orifice of the second or each additional molding tool can be adjusted in accordance with the modified cross-section of the depression of the carrier foil.
According to a further beneficial specific embodiment, at least one device is provided for preheating at least one of the foils or layers before the calender. The temperature of said heating device is selected conditional upon the properties of the to be heated foil, such as for example thickness and type of the thermoplastic synthetic material. The preheating preferably takes place by means of an IR radiant [heating] field.
Further beneficial refinements of the invention are apparent from the sub claims 2 to 6, 8 to 17 and 20.